Representation of microscale ocean wavenumber spectrum correct to the second order

In this paper, the analytical representations of four wave source functions in high-frequency spectrum range are given on the basis of ocean wave theory and dimensional analysis, and the perturbation method is used to solve the governing equations of ocean wave high-frequency spectrum on the basis of the temporally stationary and locally homogeneous scale relations of microscale wave. The microscale ocean wavenumber spectrum correct to the second order has an explicit structure, its first order part represents the equilibrium between different source functions, and its second order part represents the contribution of microscale wave propagation.

On the nonlinear integral transform of an ocean wave spectrum into an along-track interferometric synthetic aperture radar image spectrum

We present a new nonlinear integral transform relating the ocean wave spectrum to the along-track interferometric synthetic aperture radar (AT-INSAR) image spectrum. The AT-INSAR, which is a synthetic aperture radar (SAR) employing two antennas displaced along the platform's flight direction, is considered to be a better instrument for imaging ocean waves than the SAR. This is because the AT-INSAR yields the phase spectrum and not only the amplitude spectrum as with the conventional SAR. While the SAR and AT-INSAR amplitude spectra depend strongly on the modulation of the normalized radar cross section (NRCS) by the long ocean waves, which is poorly known, the phase spectrum depends only weakly on this modulation. By measuring the phase difference between the signals received by both antennas, AT-INSAR measures the radial component of the orbital velocity associated with the ocean waves, which is related to the ocean wave height field by a well-known transfer function. The nonlinear integral transform derived in this paper differs from the one previously derived by Bao et al. [1999] by an additional term containing the derivative of the radial component of the orbital velocity associated with the long ocean waves. By carrying out numerical simulations, we show that, in general, this additional term cannot be neglected. Furthermore, we present two new quasi-linear approximations to the nonlinear integral transform relating the ocean wave spectrum to the AT-INSAR phase spectrum.

Outer wave number spectrum and statistical distribution of apparent wave number vector

Based on the ray theory and Longuet-Higgins's linear,model of sea waves, the joint distribution of wave envelope and apparent wave number vector is established. From the joint distribution, we define a new concept, namely the outer wave number spectrum, to describe the outer characteristics of ocean waves. The analytical form of the outer wave number spectrum, the probability distributions of the apparent wave number vector and its components are then derived. The outer wave number spectrum is compared with the inner wave number spectrum for the average status of wind-wave development corresponding to a peakness factor P = 3. Discussions on the similarity and difference between the outer wave number spectrum and inner one are also presented in the paper. (C) 2002 Elsevier Science Ltd. All rights reserved.

Three dimensional fluorescence excitation-emission on matrix spectrum of dissolved organic substance in marine microalgaes growth process

The three-dimensional fluorescence spectrum was used to detect the changes in dissolved organic substances from the cultured Skeletonema costatum, Alexandrium tamarense, Alexandrium mimutum, Scrippsiella trochodea, Prorocentrum donghaiense and Prorocentrum micans. The result indicates that all of the microalgaes can produce FDOM in the growth courses. Diatom such as Skeletonema costatum can produce humic-like FDOM. However dinoflagellate can produce protein-like FDOM at exponential growth phase. When the algae grows into decadency phase, the intensity of humic-like and protein-like fluorescence augments rapidly, which may be due to a mass of FDOM realeased by the old or dead cell fragmentation and the degradation of bacteria by using non-FDOM. The fluorescent intensity of Alexandrium tamarense, Alexandrium mimutum, Prorocentrum donghaiense and Prorocentrum micans can reduce at anaphase of decadency phase because of the degradation of bacteria and light. The same genus of algae can produce similar FDOM, for example: Alexandrium tamarense, and Alexandrium mimutum, Prorocentrum donghaiense and Prorocentrum micans, but the positions of the fluorescence peaks are different.

Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes

Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

多尺度分解与相位反褶积提高海上地震资料分辨率和信噪比

Offshore seismic exploration is full of high investment and risk. And there are many problems, such as multiple. The technology of high resolution and high S/N ratio on marine seismic data processing is becoming an important project. In this paper, the technology of multi-scale decomposition on both prestack and poststack seismic data based on wavelet and Hilbert-Huang transform and the theory of phase deconvolution is proposed by analysis of marine seismic exploration, investigation and study of literatures, and integration of current mainstream and emerging technology. Related algorithms are studied. The Pyramid algorithm of decomposition and reconstruction had been given by the Mallat algorithm of discrete wavelet transform In this paper, it is introduced into seismic data processing, the validity is shown by test with field data. The main idea of Hilbert-Huang transform is the empirical mode decomposition with which any complicated data set can be decomposed into a finite and often small number of intrinsic mode functions that admit well-behaved Hilbert transform. After the decomposition, a analytical signal is constructed by Hilbert transform, from which the instantaneous frequency and amplitude can be obtained. And then, Hilbert spectrum. This decomposition method is adaptive and highly efficient. Since the decomposition is based on the local characteristics of the time scale of data, it is applicable to nonlinear and non-stationary processes. The phenomenons of fitting overshoot and undershoot and end swings are analyzed in Hilbert-Huang transform. And these phenomenons are eliminated by effective method which is studied in the paper. The technology of multi-scale decomposition on both prestack and poststack seismic data can realize the amplitude preserved processing, enhance the seismic data resolution greatly, and overcome the problem that different frequency components can not restore amplitude properly uniformly in the conventional method. The method of phase deconvolution, which has overcome the minimum phase limitation in traditional deconvolution, approached the base fact well that the seismic wavelet is phase mixed in practical application. And a more reliable result will be given by this method. In the applied research, the high resolution relative amplitude preserved processing result has been obtained by careful analysis and research with the application of the methods mentioned above in seismic data processing in four different target areas of China Sea. Finally, a set of processing flow and method system was formed in the paper, which has been carried on in the application in the actual production process and has made the good progress and the huge economic benefit.

空间电流体系地磁反演及理论研究

The space currents definitely take effects on electromagnetic environment and also are scientific highlight in the space research. Space currents as a momentum and energy provider to Geospace Storm, disturb the varied part of geomagnetic field, distort magnetospheric configuration and furthermore take control of the coupling between magnetosphere and ionosphere. Due to both academic and commercial objectives above, we carry on geomagnetic inverse and theoretical studies about the space currents by using geomagnetic data from INTERMAGNET. At first, we apply a method of Natural Orthogonal Components (NOC) to decomposition the solar daily variation, especially for (solar quiet variation). NOC is just one of eign mode analysis, the most advantage of this method is that the basic functions (BFs) were not previously designated, but naturally came from the original data so that there are several BFs usually corresponding to the process really happened and have more physical meaning than the traditional spectrum analysis with the fixed BFs like Fourier trigonometric functions. The first two eign modes are corresponding to the and daily variation and their amplitudes both have the seasonal and day-to-day trend, that will be useful for evaluating geomagnetic activity indices. Because of the too strict constraints of orthogonality, we try to extend orthogonal contraints to the non-orthogonal ones in order to give more suitable and appropriate decomposition of the real processes when the most components did not satisfy orthogonality. We introduce a mapping matrix which can transform the real physical space to a new mathematical space, after that process, the modified components which associated with the physical processes have satisfied the orthogonality in the new mathematical space, furthermore, we can continue to use the NOC decomposition in the new mathematical space, and then all the components inversely transform back to original physical space, so that we would have finished the non-orthogonal decomposition which more generally in the real world. Secondly, geomagnetic inverse of the ring current’s topology is conducted. Configurational changes of the ring current in the magnetosphere lead to different patterns of disturbed ground field, so that the global configuration of ring current can be inferred from its geomagnetic perturbations. We took advantages of worldwide geomagnetic observatories network to investigate the disturbed geomagnetic field which produced by ring current. It was found that the ring current was not always centered at geomagnetic equator, and significantly deviated off the equator during several intense magnetic storms. The deviation owing to the tilting and latitudinal shifting of the ring current with respect to the earth’s dipole can be estimated from global geomagnetic survey. Furthermore those two configurational factors which gave a quantitative description of the ring current configuration, will be helpful to improve the Dst calibration and understand the dependence of ring current’s configuration on the plasma sheet location relative to the equator when magnetotail field warped. Thirdly, the energization and physical acceleration process of ring current during magnetic storm has been proposed. When IMF Bz component increase, the enhanced convection electric field drive the plasma injection into the inner magnetosphere. During the transport process, a dynamic heating is happened which make the particles more ‘hot’ when the injection is more deeply inward. The energy gradient along the injection path is equivalent to a kind of force, which resist the plasma more earthward injection, as a diamagnetic effect of the magnetosphere anti and repellent action to the exotically injected plasma. The acceleration efficiency has a power law form. We use analytical way to quantitatively describe the dynamical process by introducing a physical parameter: energization index, which will be useful to understand how the particle is heated. At the end, we give a scheme of how to get the from storm time geomagnetic data. During intense magnetic storms, the lognormal trend of geomagnetic Dst decreases depend on the heating dynamic of magnetosphere controlling ring current. The descending pattern of main phase is governed by the magnetospheric configuration, which can be describled by the energization index. The amplitude of Dst correlated with convection electric field or south component of the solar wind. Finally, the Dst index is predicted by upstream solar wind parameter. As we known space weather have posed many chanllenges and impacts on techinal system, the geomagnetic index for evaluating the activity space weather. We review the most popular Dst prediction method and repeat the Dst forecasting model works. A concise and convnient Key Points model of the polar region is also introduced to space weather. In summary, this paper contains some new quantitative and physical description of the space currents with special focus on the ring current. Whatever we do is just to gain a better understanding of the natural world, particularly the space environment around Earth through analytical deduction, algorithm designing and physical analysis, to quantitative interpretation. Applications of theoretical physics in conjunction with data analysis help us to understand the basic physical process govering the universe.

HHT在电磁信号处理中的应用

In modem signal Processing，non－linear，non－Gaussian and non－stable signals are usually the analyzed and Processed objects，especially non－stable signals. The convention always to analyze and Process non－stable signals are： short time Fourier transform，Wigner－Ville distribution，wavelet Transform and so on. But the above three algorithms are all based on Fourier Transform，so they all have the shortcoming of Fourier Analysis and cannot get rid of the localization of it. Hilbert－Huang Transform is a new non－stable signal processing technology，proposed by N. E. Huang in 1998. It is composed of Empirical Mode Decomposition (referred to as EMD) and Hilbert Spectral Analysis (referred to as HSA). After EMD Processing，any non－stable signal will be decomposed to a series of data sequences with different scales. Each sequence is called an Intrinsic Mode Function (referred to as IMF). And then the energy distribution plots of the original non－stable signal can be found by summing all the Hilbert spectrums of each IMF. In essence，this algorithm makes the non－stable signals become stable and decomposes the fluctuations and tendencies of different scales by degrees and at last describes the frequency components with instantaneous frequency and energy instead of the total frequency and energy in Fourier Spectral Analysis. In this case，the shortcoming of using many fake harmonic waves to describe non－linear and non－stable signals in Fourier Transform can be avoided. This Paper researches in the following parts： Firstly，This paper introduce the history and development of HHT，subsequently the characters and main issues of HHT. This paper briefly introduced the basic realization principles and algorithms of Hilbert－Huang transformation and confirms its validity by simulations. Secondly, This paper discuss on some shortcoming of HHT. By using FFT interpolation, we solve the problem of IMF instability and instantaneous frequency undulate which are caused by the insufficiency of sampling rate. As to the bound effect caused by the limitation of envelop algorithm of HHT, we use the wave characteristic matching method, and have good result. Thirdly, This paper do some deeply research on the application of HHT in electromagnetism signals processing. Based on the analysis of actual data examples, we discussed its application in electromagnetism signals processing and noise suppression. Using empirical mode decomposition method and multi-scale filter characteristics can effectively analyze the noise distribution of electromagnetism signal and suppress interference processing and information interpretability. It has been founded that selecting electromagnetism signal sessions using Hilbert time-frequency energy spectrum is helpful to improve signal quality and enhance the quality of data.

东海陆架盆地西南部烟囱构造与油气运聚关系研究

In recent years, chimney structure has been proved one of important indicators and a useful guide to major petroleum fields exploration through their exploration history both at home and abroad. Chimney structure, which has been called "gas chimney" or "seismic chimney", is the special fluid-filled fracture swarm, which results from the boiling of active thermal fluid caused by abruptly decreasing of high pressure and high temperature in sedimentary layers of upper lithosphere. Chimney structure is well developed in continental shelf basin of East China Sea, which indicates the great perspectives of petroleum resources there. However, the chimney structure also complicated the petroleum accumulation. So the study of chimney structure on its formation, its effect on occurrence and distribution of petroleum fields is very important not only on theoretical, but also on its applied research. It is for the first time to make a clear definition of chimney structure in this paper, and the existence and practical meaning of chimney structure are illustrated. Firstly, on the viewpoint of exploration, this will amplify exploration area or field, not only in marine, but also on continent. Secondly, this is very important to step-by-step exploration and development of petroleum fields with overpressure. Thirdly, this will provide reference for the study on complex petroleum system with multi-sources, commingled sources and accumulation, multi-stage accumulations, and multi-suits petroleum system in the overlay basin. Fourthly, when the thermal fluid enters the oceanic shallow layer, it can help form gas hydrate under favorable low-temperature and high-pressure conditions. Meanwhile, the thermal fluid with its particular component and thermal content will affect the physical, chemical and ecological environments, which will help solving the problem of global resources and environment. Beginning from the regional tectonic evolution characteristics, this paper discussed the tectonic evolution history of the Taibei depression, then made an dynamical analysis of the tectonic-sedimentary evolution during the Mesozoic and Cenozoic for the East China Sea basin. A numerical model of the tectonic-thermal evolution of the basin via the Basin-Mod technique was carried out and the subsidence-buried history and thermal history of the Taibei depression were inverse calculated: it had undergone a early rapid rift and sag, then three times of uplift and erosion, and finally depressed and been buried. The Taibei depression contains a huge thick clastic sedimentary rock of marine facies, transitional facies and continental facies on the complex basement of ante-Jurassic. It is a part of the back-arc rifting basins occurred during the Mesozoic and Cenozoic. The author analyzed the diagenesis and thermal fluid evolution of this area via the observation of cathodoluminescence, scanning electron microscope and thin section, taking advantage of the evidences of magma activities, paleo-geothermics and structural movement, the author concluded that there were at least three tectonic-thermal events and three epochs of thermal-fluid activities; and the three epochs of thermal-fluid activities were directly relative to the first two tectonic-thermal events and were controlled by the generation and expulsion of hydrocarbon in the source rock simultaneously. Based on these, this paper established the corresponding model between the tectonic-thermal events and the thermal-fluid evolution of the Taibei Depression, which becomes the base for the study on the chimney structures. According to the analyses of the gas-isotope, LAM spectrum component of fluid inclusion, geneses of CO_2 components and geneses of hydrocarbon gases, the author preliminarily verified four sources of the thermal fluid in the Taibei Depression: ① dehydration of mud shale compaction, ② expulsion of hydrocarbon in the source rock; ③ CO_2 gas hydro-thermal decomposition of carbonatite; ④magma-derived thermal fluid including the mantle magma water and volatile components (such as H_2O, CO_2, H_2S, SO_2, N_2 and He etc.). On the basis of the vitrinite reflectance (Ro), homogenization temperature of fluid inclusion, interval transit time of major well-logging, mud density of the wells, measured pressure data and the results of previous studies, this paper analyzed the characteristics of the geothermal fields and geo-pressure fields for the various parts in this area, and discussed the transversal distribution of fluid pressure. The Taibei depression on the whole underwent a temperature-loss process from hot basin to cold basin; and locally high thermal anomalies occurred on the regional background of moderate thermal structure. The seal was primarily formed during the middle and late Paleocene. The overpressured system was formed during the middle and late Eocene. The formation of overpressured system in Lishui Sag underwent such an evolutionary process as "form-weaken-strengthen-weaken". Namely, it was formed during the middle and late Eocene, then was weakened in the Oligocene, even partly broken, then strengthened after the Miocene, and finally weakened. The existence of the thermal fluid rich in volatile gas is a physical foundation for the boiling of the fluid, and sharply pressure depletion was the major cause for the boiling of the fluid, which suggests that there exists the condition for thermal fluid to boil. According to the results of the photoelastic simulation and similarity physical experiments, the geological condition and the formation mechanism of chimnestructures are summarized: well compartment is the prerequisite for chimney formation; the boiling of active thermal fluid is the original physical condition for chimney formation; The local place with low stress by tension fault is easy for chimney formation; The way that thermal fluid migrates is one of the important factors which control the types of chimney structures. Based on where the thermal fluid come from and geometrical characteristics of the chimney structures, this paper classified the genetic types of chimney structures, and concluded that there existed three types and six subtypes chimney structures: organic chimney structures generated by the hydrocarbon-bearing thermal fluid in middle-shallow layers, inorganic and commingling-genetic chimney structures generated by thermal fluid in middle-deep layers. According to the seismic profiles interpretations, well logging response analysis and mineralogical and petrological characteristics in the study area, the author summarized the comprehensive identification marks for chimney structures. Especially the horizon velocity analysis method that is established in this paper and takes advantage of interval velocity anomaly is a semi-quantitative and reliable method of chimney structure s identification. It was pointed out in this paper that the occurrence of the chimney structures in the Taibei depression made the mechanism of accumulation complicated. The author provided proof of episodic accumulation of hydrocarbon in this area: The organic component in the boiling inclusion is the trail of petroleum migration, showing the causality between the boiling of thermal fluid and the chimney structures, meanwhile showing the paroxysmal accumulation is an important petroleum accumulation model. Based on the evolutionary characteristics of various types of chimney structures, this paper discussed their relationships with the migration-accumulation of petroleum respectively. At the same time, the author summarized the accumulating-dynamical models associated with chimney structures. The author analyzed such accumulation mechanisms as the facies state, direction, power of petroleum migration, the conditions of trap, the accumulation, leakage and reservation of petroleum, and the distribution rule of petroleum. The author also provides explanation for such practical problems the existence of a lot of mantle-derived CO_2, and its heterogeneous distribution on plane. By study on and recognition for chimney structure, the existence and distribution of much mantle-derived CO_2 found in this area are explained. Caused by tectonic thermal activities, the deep magma with much CO_2-bearing thermal fluid migrate upward along deep fault and chimney structures, which makes two wells within relatively short distance different gas composition, such as in well LF-1 and well LS36-1-1. Meanwhile, the author predicted the distribution of petroleum accumulation belt in middle-shallow layer for this area, pointed out the three favorable exploration areas in future, and provided the scientific and deciding references for future study on the commingling-genetic accumulation of petroleum in middle-deep layer and the new energy-gas hydrate.